1. Field of the Invention
This invention relates to a heat pipe heat exchanger that recovers the heat of hot gas exhausted from the devices such as thermal power plants into the lower thermal gas.
2. Description of the Prior Art
Because of the bulkiness of exchangers both in terms of its manufacturing process and material, it is prevailing for the heat pipes of this type of heat pipe heat exchangers, to have spiral fins. The heat pipes with spiral fins ar installed in many rows in a casing that is divided into two sections by a vertical divider plate, namely into the hot gas flow duct and the cold gas flow duct. Through the divider plate penetrates each heat pipe so that an end of each pipe is exposed to the hot gas flow while the other end to the cold gas flow. The heat pipes in the hot gas flow duct are installed horizontally a little slanted so that they can recover and transfer the heat of the exhausted hot gas that pass through the hot gas flow duct to the cold gas that pass through the cold gas flow duct.
Generally, the winding direction of the spiral fins are decided in accordance with the specifications of high frequency welding machine manufacturing the fins. As the most of the present day's welding machines are designed to weld the fins clockwise, most of the heat pipes of this type of heat exchangers are with fins winding clockwise. Further, as the winding direction of the fins does not matter the effectiveness of the heat pipes itself with regard to the heat exchange capacity, no attention was paid to the winding direction of the fins used for this type of heat exchangers.
As the dust present in the exhausted hot ga that deposit on the heat pipes with spiral fins may cause impairment of the thermal efficiency of the heat exchanger, so called shot cleaning process has been recommended and employed prevailingly, which eliminates the dust deposited on the heat pipes with spiral fins by means of a number of small steel balls falling on and colliding with the bank of heat pipes.
The reason why the spiral fins heat pipes are positioned a little slanted horizontally so as to have an end of each pipe in the hot gas flow duct becomes lower than the other end is to accelerate the flow-back of the heat medium in the heat pipes. 1n the conventional type of heat exchangers, as mentioned above, no attention was paid to the winding direction of the spiral fins provided around the heat pipes. For example, as viewed in FIG. 5, which is a partial sectional view of a conventional heat pipe heat exchanger, each heat pipe 1 is slightly slanted so that this side in FIG. 5 of the heat pipes comes lower and the spiral fins 11 are slightly facing upward and therefore, more steel balls are inclined to bounce to the left direction in FIG. 5 colliding with the spiral fins 11, thus, as shown by arrows in FIG. 5, more steel balls fall down to the same direction as the fins' slope face and therefore, the lower the rows, the more balls are gathered basically to the left side in FIG. 5 resulting in an insufficient cleaning in the below right area in FIG. 5 of the heat pipes. This tendency increases all the more the larger in scale the heat exchangers are.